Various vacuum treatments in vacuum are essential in the production of semiconductor elements such as an integrated circuit (IC), a light emitting diode (LED), etc. For instance, film-formation for the formation of a semiconductor and etching thereof are carried out in the production of an IC. Such film-formation and etching are required to be carried out in a clean space. For this, prior to commencement of respective reaction processes, it is necessary to sufficiently evacuate a vacuum treating chamber to be in a clean state and to prevent the evacuated vacuum treating chamber from being contaminated with impurities such as atmospheric components.
In view of this, there has been proposed such a vacuum treating apparatus as shown in FIG. 10.
The vacuum treating apparatus shown in FIG. 10 comprises a substrate treating chamber 1000 and a substrate supplying chamber 1002. The substrate supplying chamber 1002 is connected through a vacuum valve 1001 comprising an O-ring made of an elastomer to the treating chamber 1000.
A substrate transporting system 1003 is connected to the substrate supplying chamber 1002, and the substrate transporting system 1003 is provided with a substrate supporting device 1004. The substrate supporting device 1004 is configured such that a substrate can be transported into the treating chamber 1000 under a vacuum condition. The treatment of the substrate in the vacuum treating apparatus is performed in the following manner. That is, a substrate to be treated is entered in the substrate supplying chamber 1002 through the substrate supporting device 1004, followed by sufficiently evacuating the substrate supplying chamber 1002. Then, the substrate is transported into the treating chamber 1000 by opening the vacuum valve 1001 and operating the substrate transporting system 1003. Thereafter, film formation or etching treatment is performed to the substrate in the treating chamber 1000. For this apparatus, in order to prevent the treating chamber 1000 from being contaminated with atmospheric air and to maintain the inside of the treating chamber 1000 in a clean state at the time of entering the substrate in the substrate supplying chamber 1002, the inside of the treating chamber 1000 is required to be maintained in a vacuumed state. For this, the substrate supplying chamber 1002 is isolated from the treating chamber 1000 through the vacuum valve 1001 comprising the O-ring made of an elastomer.
Now, the elastomer member to be used for the vacuum valve of the vacuum apparatus releases impurity gases such as CH.sub.4, H.sub.2 O, CO.sub.2, etc. which usually cause negative effects for the vacuum process under vacuum environment. For example, in the case of the film-forming process for a Si semiconductor, when CH.sub.4, CO.sub.2, etc. are adhered to the surface of a Si film, there is caused SiC, and when H.sub.2 O is adhered, there is caused SiO. As a result, the resulting device becomes such that it is poor in characteristics or is accompanied with increased defects. In consequence, it is desired not to use an elastomer in the treating chamber 1000. Thus, there have been made proposals of replacing the elastomer by other members.
Specifically, as a first example, there is a proposal of using a metal wire instead of the above elastomer. In this case, sealing is performed by using a soft metal (sealing metal wire) and a hard metal (stainless steel for the valve seat and valve element) in combination and utilizing a permanent deformation of the soft metal caused upon contact of the valve seat with the valve element. However, such permanent deformation of the soft metal easily reaches a deformation limit in a narrow circular contacting portion between the valve seat and the valve element and because of this, there is a problem that the life of the valve is shortened. Further, there is also a problem that the sealed surface is apt to be damaged with dust or the like to cause contamination of gases. For these reasons, the valve in which a metal wire is used is poor in durability, and its application is limited to a specific use purpose.
As a second example, there is a proposal of using a springy copper alloy or stainless steel as a sealing member. This proposal is to perform sealing utilizing the springing property among the hard alloys. Accordingly, in this case, there is an advantage that the life of the valve is prolonged upon use in a deformation extent less than the elastic limit of the sealing member. However, there is a problem that it is remarkably costly to seal the entire circular contacting portion without leaving any space, since the roughness and the degree of parallelization for the sealing face of each of the sealing members, valve seat and valve element are necessary to be treated with extreme precision. Further, it is necessary to make the imposing pressure markedly large in order to completely seal the entire sealing face since the springing property of a hard metal is utilized. In addition, as well as in the case of the first example, dust deposited on the sealing face is apt to cause damage. In addition to these problems, there is also other problem that although the durability against repetition of opening and closing is good, its handling is difficult and it is costly.
As a third example, there is proposed a double sealing type valve having the structure shown in FIG. 9 by Unexamined Japanese Patent Publication 59(1984)-17302. This is configured such that not only sealing efficiency is improved but also gases released from the elastomer due to vacuum environment are properly treated by way of performing double sealing with the use of a metal sealing member and an elastomer sealing member, and performing gas exhaustion through the intermediate space between them. Shown in FIG. 9 is a view in which the sealed portion of the valve element is enlarged. In this figure, the valve is in an opened state.
In the case of the valve shown in FIG. 9, a valve element 901 is provided with an elastomer sealing member 904, and elastomer seal 905 is formed by pressing the elastomer sealing member 904 to a valve seat 902. And, metal seal 903 is formed by pressing a plane face of the valve element 901 to a plane face of the valve seat 902. There is formed an intermediate space 906 between the elastomer sealing member 904 and the metal seal 903. This intermediate space 906 is connected to an exhaust pump 908 externally positioned through a passageway 907 being connected to said intermediate space. And, gas released from the elastomer sealing member 904 is exhausted through the intermediate space 906 by means of the exhaust pump 908.
For this third example, there is an advantage that repetition durability and resistance to dust are good. However, there is a problem that the apparatus obtained becomes unavoidably costly because it is necessary to provide the exhaust pump 908 as an external device and it is required to form the passageway 907 in the valve seat 902. In addition, there is also a problem for this vacuum valve that the elastomer seal 905 is unavoidably formed as the metal seal 903 is formed, and because of this, deformation and deterioration are markedly caused on the elastomer sealing member 904, wherein should the elastomer sealing member be replaced by a new one, it takes a period of some tens hours in order to depressurize from atmospheric pressure to the original ultra-high vacuum state in the case of a ultra-high vacuum treating apparatus.